R-22 was so popular for several decades because it offered an excellent combination of thermodynamic performance, safety, and cost that made it ideal for residential and commercial air conditioning. Introduced in the 1950s as a replacement for more toxic and flammable refrigerants like ammonia, sulfur dioxide, and methyl chloride, R-22 had good energy efficiency, moderate operating pressures suitable for small compressors, good heat transfer properties, and compatibility with mineral oil lubricants, making systems simple and reliable. It had low toxicity classified as A1, non-flammable, and was relatively cheap to produce in large quantities. It worked well across a wide temperature range for air conditioning and heat pumps, with reasonable capacity and coefficient of performance. Equipment using R-22 was mass produced, technicians were trained on it, and parts were widely available, creating a large installed base. Before environmental concerns about ozone depletion became prominent, R-22 was considered a safe, efficient, and economical choice. It dominated residential central air conditioning from the 1960s until 2010, when phase-out began due to its ozone depletion potential of 0.05 and high global warming potential, leading to transition to R-410A and now R-32 and R-454B.
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